Having problem making and recieving calls in Dubai, U.A.E

Hi,

So i bought my motorola krzr k1 unlocked on ebay, and it was working fine with the sim on roaming while i was in America. Upon getting back home i was able to make a couple of calls, very briefly, but after that i cant make any calls or recieve any calls to my phone. The network id shows up i have tried changing the network settings and the phone finds the network i am on. But the same problem occurs, i have tried transferring sims from another network into my phone and the same thing happens, i can make a couple of calls but after about 30 secs the phone says call failed and the phone doesnt recieve calls either. I have no clue why this is happening!! Is it a problem with the phone as in hardware issue or is it just not completely unlocked?..



P.S: I am not looking for unlock codes or help to unlock the phone.. i just want to know where the problem lies..



Thanks.